This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The Anaphase Promoting Complex (APC) is a multiprotein E3 ubiquitin ligase that controls cell division by promoting ubiquitin-mediated proteolysis of key cell cycle regulatory proteins. The importance of the folding and assembly of APC subunits is underscored by the fact that many of their genes were identified in classic screens for cell division cycle (Cdc) mutants in S. cerevisiae and S. pombe. The ~13 APC subunits can be broadly divided into subcomplexes, one of which contains a cullin subunit and a RING subunit, making the APC a distal member of the largest family of E3 ubiquitin ligases, the Cullin-RING ligases. Another subcomplex contains the small heat shock protein CDC26 and multiple proteins containing tetratricopeptide (TPR) motifs. Other APC subcomplexes contain fewer motifs to indicate their structure and/or function. We are studying the structure and function of the APC.